Cathode ray device



IN VENT OR. J-[ans ricllxrllm ATTORNEY.

Patented Feb. 6, 1940 CATHODE RAY DEVICE.

Hans Erich Hollmann, Berlin-Lichterfelde, Ger-' many, assignor to Radio Patents Oorp.', New York, N. Y., a corporation of New York Application April 30, 1937, Serial No. 139,913 In Germany May 23, 1936 6 Claims.

The present invention relates to cathode ray tubes as used'for oscillographic recording and like purposes; and is more particularly concerned with an improved construction for and method of operating tubes of this character.

The known cathode ray tubes used for oscillographic and like purposes usually comprise means for producing a concentrated beam or pencil of electrons, a fluorescent screen arranged for the electron beam to strike against to produce a luminous recording spot thereon, and an arrangement such as a pair of electrostatic deflecting plates or magnetic field coils for deflecting the electron beam in accordance with variations of an electric controlling potential or current to obtain a visual record upon the fluorescent screen.

As is well known, the sensitivity ofdeflection of the electron beam in a cathode ray. tube of the above character employing a pair of electro- 53!) static deflecting plates may be expressed by the following theoretical equation:

wherein s represents the deflection of the luminous recording spot onthe screen from its central or zero position; E is the deflecting voltage impressed uponthe deflecting plates; l is the of the "deflecting. field and the-distanceL between 4.: the deflecting field and the fluorescent screen.

This distance L is fixed by the. size of the tube on the onelhand and by the space. occupied by the.v cathode. and the acceleration or electron lens arrangement on the other hand plus an additional spacing distance between the-electron lens and the deflecting arrangements. Furthermore, it is seen that no advantage is gained by'an excessive increase of the length l of the deflecting. plates since such an increase results in a decrease of the distance L. Moreover, a minimum distance d is required between the deflecting plates to allow the electron beam to sweepover the entire. useful, effective area of the screen and to prevent a cutting off of the beam in its extreme deflecting positions. Similar limitations apply to a tube using a magnetic instead of an electrostatic deflecting field.

' The sensitivity of deflection of the-luminescent spot in a cathode ray tube by a controlling potential or current is thus limited and it has not been possible to increase. the sensitivity beyond the limit value determined by the geometry of the tubes constructed in amanner known in the prior art.

Accordingly, an object of the invention is the l3.

in place of a round beam orv pencil used in the conventional type of cathode ray oscillographs. Such a beam produces a luminous streak or line of, light upon the fluorescent screen which is displaced. parallel to its length by means of a suitable deflectingarrangement for the electron.

beam, such as a pair of electrostatic deflecting plates connected to the source of the controlling potential or current. In order to obtain a luminous recording spot there is further provided in accordance with'the invention, a screen or mask having a slit or the equivalent thereof arranged at an angle with the flat electron beam or line.

of lightproduced thereby upon-the luminescent screen. In this manner, only a luminous spot or point is produced upon'the. recording screen 4" at the intersection of the line of light with the slit or its equivalent, whichspot will move along the slit as the: electron beam isdeflected in the manner set forth hereinbefore.

Alternatively;-the.-screen'may be coated with the. streak or line. of luminescent material arranged at an.angle-withtheJineof-light produced thereon by theelectron beam.

Further objects and featuresof the invention will bmome more: apparent from the following 5 detailed description taken with reference tothe accompanying drawing. forming. part of this specification and wherein:

Figure 1 illustrates schematically a cathode ray tube. anda recording system therefor constructed in accordance with the invention, and

Figure 2 is a side view of the tube shown in Figure 1.

Referring to the drawing, there is shown a cathode ray tube comprising an evacuated vessel or envelope in enclosing a cathode II which in the example shown has the form of a wire wound into a narrow spiral and heated to electron emitting temperature in any suitable manner such as by means of a heating battery l2. cathode is surrounded by a frame l3 havingan open front and serving as an initial concentra tion electrode to produce a. flat, electronbeam leaving the cathode such,as indicated by the dotted lines in the drawing. For this purpose the frame I3 is negatively biased in a known manner with respect to the cathode such as by means of a biasing battery or the like as shown at M. The flat electron beam after leaving the cathode is accelerated and focused upon the fluorescent screen 23 arranged at the opposite end of the tubejsuch as by means'of a pair of accelerating "or anode electrodes I5 and lfi'having slits arranged inline with the cathode or electron beam produced thereby and biased positively with respect to the cathodeby means of an anode battery IT or the like. 7 n'ected tc-a lower potential point on the battery l1 than the anode {6 whereby both anodes from what is known as an electron lens adapted to connected with" the source of deflecting potential tobe connected to the input terminals 2|. As is understood, any other well known deflecting arrangement such as a pair of magnetic deflecting coils may be provided in place of electrostatic defle'cting plates for the purpose of the invention.

There is further'provided, in accordance with the invention, ascreen or mask 22 arranged in front of or behind the fluorescent screen 23 of the tube and having a slit shown at 24. In the example illustrated, the .mask 22 is mounted qagainstthe outer wall of the tube and the slit 24 is arranged in a vertical direction in which case the cathode, electron lens, and deflecting plates have to be mounted in such a manner that the fiat electron beam forms an angle with a vertical line. Thus', theline of light l8 when defiectedin the manner described, intersects the slit 24 at different points thereby producing a recording spot which travels up and down in accordance with'the variations of the deflecting potentials impressed upon the deflecting plates. The width of the slit 24 is preferably, although not necessarily, equal to' the thickness'of the electron beam or width'of the luminous line 18 produced thereby to obtain a recordingspot resembling as much as :possible a-circle as obtained in the ordinary type'of cathode ray tube." In thefexample illustrated, the. line H3 in the'zero position intersects the slit 24 at its center whereby both positive and negative potential variations may he recorded with regard to a zero lineor axis." If the beam is deflected, the'luminous line will assume'varyi'ng positions within the'useful deflecting range between the extreme positions shown at I 8 and I8".

In order to produce a permanent oscillographic The The anode I5 is con record, the spot thus produced on the luminescent screen may be focused in a known manner upon the photographic film 25 or the like by means of an optical lens 26. The film 25 is moved continuously in a direction at right angle to the slit 24 v as indicated by the arrow to provide a time axis for the curve or record obtained, and indicated at 21. As is understood, the movement of the film 25 may be in a direction forming an angle with the slit 24 difi'eringfrom a rightangle i'f a record is desired in a coordinate system other than rectangular coordinates, as in the case illustrated. It is further understood that any other arrangement of known type for producing a fiat scribed or it may consist of a coating of lacquer. or'othe'r material opaque to'light rays (if the,

screen is mounted against the outside wall of the tube) or to electron rays if the mask is mounted against the inner wallofthe tube in front of the fluorescent screen. Alternatively, a suitable screening substance may be applied to the flour's; cent screw either before or after depositing'the fluorescent substance with a slit like portion 24' kept free by means of a stencil or the like in a manner well understood.

of the type described, it is possible to considerably increase the sensitivity of deflection of the recording spot beyond values obtainable in cathode ray tubes of standard design and construc; tion. Thus, referring to Figure 2, it is seen that if the luminous line I8 is displaced parallel to its length by an amount a from its position l8" to position I 8, the intersection point will move along the slit Z4 from-point A to point B; that isgitiwill travel a distance equal to COS 0e whereina represents the angleb'etween the J 24 and a line forming a right angle with the line H3. The equation for the deflection 5' obtained with the new tube is therefore modified by substituting the distance travelled by the luminous spot As isseenrtherefrom if 11:0 that is, ifthe s'lit 24 is arranged at a right angle to the luminous I so By'means of an arrangement and construction line, ,i 8, no increase in sensitivity is obtained since 36 angle the sensitivity obtained is 5.5 times that of an ordinary cathode ray tube. J In this manner it" is seen that the sensitivity may be increasedconsiderably as comparedwith cathodelray tubes of known construction. A limit is determined only 'bythe fact that the intersection point or re:

cording spot in the case of large angles assumes an oblong rhomboidal shape in place-of a more or less round spot which may impair the, sharpness of the record or oscillogram'obtained.

According to a further feature of the invention, the slit 24 may be given any shape differing from a straight line and following a predetermined function in order to obtain a record or oscillographic curve related to the deflecting potentials or currents in accordance with a desired law.

It will be apparent from the above that the invention is not limited to the specific constructions, arrangements of parts and methods of operation described and shown herein for illustration, but that the underlying novel concept thereof is susceptible of numerous modifications and variations coming within the broad scope and spirit of the invention as defined in the appended claims.

It is understood therefore that the description and drawing are to be regarded in an illustrative rather than in a limiting sense. 1

I claim:

1. In a cathode ray recording device, a source of electrons, means comprising an element having a narrow slit for concentrating the electrons emitted by said source into a beam of linear crosssection in line with said slit, means for deflecting said beam substantially parallel to its cross-sectional axis, a luminescent screen arranged to be impinged by said beam, and a mask overlying said screen and having a slit forming an angle with said first slit substantially differing from a right angle, thereby to produce a luminous recording spot moving across the slit of said mask in accordance with variations of a deflecting potential impressed upon said deflecting means.

2. In a cathode ray recording device, a source of electrons, means comprising at least one diaphragmatic electrode having a narrow slit for concentrating the electrons emitted by said source into a beam of linear cross-section in line with said slit, a pair of electrostatic deflecting plates arranged opposite and parallel to said beam in its normal position, a luminescent screen arranged to be impinged by said beam, and a mask overlying said screen and having a slit forming an angle with said first slit substantially differing from a right angle, thereby to produce a luminous recording spot moving across the slit of said mask in accordance with variations of a deflecting potential impressed across said deflecting plates.

3. In a cathode ray recording device, a source of electrons, means comprising at least one diaphragmatic electrode having a narrow slit for concentrating the electrons emitted by said source into a beam of linear cross-section in line with said slit, means for deflecting said beam substantially parallel to its cross-sectional axis, a luminescent screen arranged to be impinged by said beam, and a mask overlying said screen and having a slit forming an angle with said first slit substantially differing from a right angle, the line connecting the center points of both said slits coinciding with the normal axis of said electron beam, thereby to produce a luminous recording spot moving from the center of the slit of said mask in opposite directions in dependence upon variations in a positive or negative sense, respectively, of a deflecting potential impressed upon said deflecting means.

4. In a cathode ray recording device, a source of electrons, means comprising at least one diaphragmatic electrode having a narrow slit for concentrating the electrons emitted by said source into a beam of linear cross-section in line with said slit, means for deflecting said beam substantially parallel to its cross-sectional axis, a luminescent screen, arranged to be impinged by said beam, and a mask overlying said screen and having a slit forming an angle with said first slit substantially differing from a right angle, both of said slits being of substantially equal width, thereby to produce a luminous recording spot moving across the slit of said mask in accordance with variations of a deflecting potential impressed upon said deflecting means.

5. In a cathode ray recording device, an envelope, a source of electrons disposed at one end within said envelope, means comprising at least one diaphragmatic acceleration electrode having a narrow slit for concentrating the electrons emitted by said source into a beam of linear crosssection in line with said slit, means for deflecting said beam substantially parallel to its cross-sectional axis, a translucent luminescent screen at the opposite end of said envelope impinged by said electron beam, and a mask overlying said luminescent screen and disposed on the outside of said envelope, said mask having a slit forming an angle with said first slit substantially differing from a right angle, thereby to produce a luminous recording spot moving across the slit of said mask in proportion to variations of a deflecting potential impressed upon said deflecting means.

6. In a recording system, a cathode ray device comprising an envelope, a source of electrons disposed at one end Within said envelope, means comprising at least one diaphragmatic acceleration electrode having a narrow slit for concentrating the electrons emitted by said source into a beam oi linear cross-section in line with said slit, means for deflecting said beam substantially parallel to its cross-sectional axis, a translucent luminescent screen at the opposite end of said envelope impinged by said electron beam, and a mask overlying said luminescent screen and disposed on the outside of said envelope, said mask having a slit forming an angle with said first slit substantially differing from a right angle, thereby to produce a luminous recording spot moving across the slit of said mask in proportion to variations of a deflecting potential impressed upon said deflecting means, a record carrier with means for continuously moving the same at an angle to the slit of said mask, and means for focussing the luminescent spot on said screen unto said record carrier.

HANS ERICI-I HOLLMANN. 

